Eighteen senators urged EPA in a May 20 letter to toughen mercury emissions standards at nine mercury-cell, chlor-alkali plants and to thoroughly analyze the plants’ use of the element. The nine plants are what is left of some 35 U.S. plants that once used mercury to make chlorine and sodium hydroxide. The senators also criticized EPA and the industry for failing to account for all mercury used in production. They noted that EPA acknowledged loss of some 65 tons of mercury annually in chlor-alkali manufacture (C&EN, March 15, page 31). Last December, EPA issued a final regulation to limit the plants’ mercury air emissions and was sued by the Natural Resources Defense Council (NRDC), which said the regulations are too weak. The group urged EPA to reconsider the rules. In an April letter, the agency agreed to do so, saying a new rule would be proposed within the “next several months.” EPA staff said it was unlikely the regulation would be reproposed before late summer or fall. The Chlorine Institute blames election year politics for the criticisms and says only approximately 5 tons are emitted to air. It also says industry has voluntarily reduced its mercury use by 74% since 1996.